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From:James Montebello Date:January 11 2002 7:31pm
Subject:Re: Database Size Limit
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This is speculation:

They're slower because many operations have to be done using 64 bit
values rather than 32 bit values.  You set the flag by setting the max
data size when creating the table.  You can also alter this after the
table is created with ALTER TABLE.  The doc suggests you're setting the
actual maximum size, but if you set the size to even 1 byte past 4GB
(at least on Solaris), it immediately flips to a value way above 4GB,
which is probably the Solaris limit (may be 2TB, I forget).  Not sure
what it does on Linux.

We saw a significant performance decrease on Solaris when we tried to
use max table sizes above 4GB, and assume it's because of an internal
switch from 32-bit pointers to 64-bit pointers.  May not make nearly as
much of a performance difference on a real 64-bit processor and OS.

james montebello

On Fri, 11 Jan 2002, Aaron Brick wrote:

> > Yes and no.  With 3.23, the MyISAM format will, by default, have a 4GB
> > limit (32 bits).  You can set flags on the table to allow a 64-bit table,
> > and you'll generally hit an OS or physical limitation long before you 
> > run out of space.  The downside of the 64-bit version is it's considerably
> > slower.  Better to split large datasets up into sub-4GB units. 
> 
> why are operations on the >4GB tables slower?
> 
> and, incidentally, where is that flag set?
> 
> thanks,
> 
> aaron brick.
> 
> 
>                 ________________________________________________
>                /                                                \
>               |   Aaron Brick                 (415) 206 - 4685   |
>               |   brick@stripped         Room 3501C, SFGH   |
> 
>                   Programmer Analyst, Functional Genomics Core  
>                    Sandler Center for Basic Research in Asthma
>                    Lung Biology Center, Department of Medicine
>                                 San Francisco General Hospital
>                        University of California, San Francisco
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Thread
Database Size LimitManish Mehta11 Jan
  • Re: Database Size LimitDan Nelson11 Jan
    • Re: Database Size LimitJames Montebello11 Jan
      • Re: Database Size LimitAaron Brick11 Jan
        • Re: Database Size LimitJames Montebello11 Jan
          • Re: Database Size LimitBenjamin Arai13 Jan
Re: Database Size LimitDemirchyan Oganes-AOD09811 Jan
  • Re: Database Size LimitBenjamin Arai13 Jan
    • Re: Database Size LimitAaron Brick14 Jan
      • Re: Database Size LimitJeremy Zawodny17 Jan
Re: Database Size LimitHeikki Tuuri13 Jan